300 A MANUAL OF ANATOMY. 



Nerve Supply. From the median by the anterior inter- 

 osseous (eighth cervical and first dorsal nerves). 

 Action. To flex the thumb, then the wrist. 



Plexor Profundus Digitorum. Fig. 67. 



Origin. From the anterior and inner surfaces of the 

 ulna above the pronator quadratus, from the inner and 

 upper two-thirds of the interosseous membrane, from the 

 posterior ridge of the ulna in common with the origin of 

 the flexor and extensor carpi ulnaris muscles. 



Insertion. Into the front of the bases of the last pha- 

 langes of the four fingers. 



Nerve Supply. Ulnar to the inner portion, median (an- 

 terior interosseous) to the outer portion. The filaments 

 come from the eighth cervical and first dorsal nerves. 



Action. Flexor of fingers, wrist (all the joints between 

 the lower end of the radius and the last set of interphalan- 

 geal articulations). 



DISSECTION. 



Incisions. (i) Continue the median incision down the palm and along 

 the front of the middle finger. (2) Make a transverse cut across the palm 

 near the web of the fingers. (3) Incise the skin down the front of each 

 finger. (4) Carry an incision from the front of the wrist along the palmar 

 surface of the thumb. 



Reflect the integument from the palm, thumb, and two or more fingers. 



Be very careful not to injure the palmar fascia and the digital (cutaneous) 

 vessels and nerves, which lie close under the integument. 



The palmaris brevis muscle, the palmar cutaneous branches of the median 

 and ulnar nerves, the palmar fascia, the digital and collateral digital nerves 

 and arteries are to be carefully cleaned. 



Palmaris Brevis. Fig. 65. 



Origin. From the front of the palmar fascia and an- 

 terior annular ligament. 



Insertion. Into the skin on the ulnar border of the 

 palm. 



